The Earth has a magnetic field around it, which is generated by its molten core. This magnetic field exerts a force on compass dials, which are magnets, causing them to align with the Earth's magnetic field.
This force on compass dials is an example of a force that _______.
A.
acts only on contact.
B.
needs electricity to act.
C.
acts through particles in the air.
D.
acts at a distance.